An accurate speed signal is required wherever electric motors are used for a drive whose regulation is to be carried out more precisely than using a conventional block commutation. The speed signal may be ascertained using an angle signal, which may be detected by a commutation sensor. However, the angle signal and thus also the speed signal may have disturbances which prevent precise regulation of the electric motor. In the prior art, for example, approaches are described for correcting the disturbances with the aid of a previously ascertained correction value.
DE 102 60 862 A1 shows a method for correcting an angle- and/or distance-measuring sensor system, in which sinusoidal or cosinusoidal measuring signals are evaluated, which are obtained by scanning a moved measuring object. The correction of the angle or phase errors of the measuring signals takes place by deriving constants from a plurality of measuring signals for estimating and correcting the angle error or phase error and/or the amplitude of the measuring signals.
DE 101 33 524 A1 describes a method for correcting a dynamic error of a sensor. This dynamic error superposes the sensor signal, for example, in the form of periodic fluctuations, the frequency and amplitude of which continuously change with the speed of the motor. In order to correct the dynamic error, the sensor output signal is fed to a filter circuit and a correction circuit. The correction circuit receives one or multiple filtered signals delivered by the filter circuit and generates a corrected sensor signal from information it obtains by comparing the filtered signals with the unfiltered sensor output signal or corrected signals derived therefrom.
DE 10 2011 105 502 A1 shows a method for balancing a phase offset between a rotor position sensor and a rotor position of an electrically commutated motor. In this case, the rotor position sensor measures a position of the rotor of the motor, which is activated during operation using a block commutation. The measured position is compared with an expected position. A phase offset is formed from the difference between the measured and the expected position, which is used for activating the electrically commutated motor. The position of the rotor is measured using an absolute value rotor position sensor, which is compared with a motor parameter which characterizes the expected position of the rotor.
US 2007/0043528 A1 shows a method and system for measuring a speed of a high-speed motor, a rotor period being calculated from the rotor speed of the motor or from a filtered speed of the motor and a number of points being calculated from it in a sliding average value.